Such sealing devices may be dissolvable and may be used, for example, for pressure testing, where they also will function as barriers to the reservoir, in zone isolation or in borehole workover.
It is known to use plugs of a dissolvable material, such as glass, ceramic, salt, etc., where the plug may be removed or crushed after use in such a way as to leave behind very few remnants or fragments. Such plugs of a dissolvable material, if correctly configured, are removable with or without explosives in a predictable and safe manner.
Plugs comprising one or more glass layers stacked upon or above one another maybe removed without the use of explosives by utilizing techniques that include percussion tools, spikes that are thrust into the dissolvable material, balls or other articles that serve to create tensions in the dissolvable material, or puncturing of the layer disposed between the two or more glass layers (if plugs comprise more than one glass layer), where the volume contains a film or a sheet of a material other than glass.
This layer between the two or more glass layers, comprising a firm and/or a sheet of a material other than glass, may comprise a fluid, a plastic material, a rubber material, a felt material, a paper material, glue, grease, etc. The layer may be substantially solid or entirely or partially deformable/liquid. The volume between the glass layers, which may be provided with at least one of the aforementioned materials, will enable the plug to attain the desired strength and toughness during use by providing for the uptake of loads exerted on the plug in the form of a differential pressure between the under- and upper side of the plug. This may involve accommodation of loads in the form of load transfer, load distribution, or limitation of bulging as a result of frictional forces between two or more layers of glass or other suitable dissolvable or crushable materials.
If there is one glass layer, the plug during use must attain the desired strength and toughness through provision for the uptake of loads exerted on the plug in the form of a differential pressure between the under- and upper side of the one glass layer. This means that the one glass layer must be capable of receiving the entire load, both from above and below if required, on full load accommodation.
NO321976, filed on 21 Nov. 2003, describes a glass plug comprising a plurality of layers or stratiform glass discs between which are provided layers of a material other than glass. NO321976 is the very first patent publication that describes a layered glass plug. NO321976 explains why there should be provided strata or layers, as disclosed above, between the glass discs of a material other than glass, and is included in its entirely in this document.
NO325431, filed on 23 Mar. 2006, relates to an apparatus and method for crushing a dissolvable sealing device of the aforementioned type. NO325431 employs a relief chamber and an adjustable connecting means forming a fluid communication channel between the layer, the liquid film or the volume between the glass discs and relief chamber when the adjustable connecting means is set in an open position. When the adjustable connecting means is set in an open position, the content between the glass discs is «punctured» and evacuated, and the load on (one or more of) the glass layers exceeds what they are designed to tolerate, which causes them to rupture. In addition, the apparatus according to NO325431 comprises a plurality of pin devices which are arranged to apply point load stresses on the glass layers when the connecting means is readjusted, with the pin bodies additionally serving to ensure that the glass layers rupture in a safe manner when the connecting means is reset. Thus, the intended function of NO325431 is to provide for rupture of the plug through resetting of the connecting means to an open position so that the space between the glass layers is punctured and the pressure drops drastically and quickly. The pressure support function will thereby disappear, and the glass the glass layers will be bent until they rupture and disintegrate, one by one. In addition, NO325431 discloses the possibility of arranging pins around the glass layers, where the pins are designed to produce point load stresses in the glass to weaken the strength of the glass layers. The way the pins' function is disclosed in NO325431, the pins have either a «passive» function, i.e., they are stationary and come into contact with the glass layers when these are bent or after the adjustable connecting means has been activated, or the pins are «actively» activated by means of the adjustable connecting means when it is activated, i.e., the pins are pushed against the glass layers and thereby produce point load stresses. In both cases, the point load stresses by the pins are produced as a causal effect of activation of the adjustable connecting means, since it is a precondition for the disclosed function of the plug that the space between the glass layers is punctured and the pressure falls drastically and quickly, with the glass layers thereby being bent and thus point loaded or, alternatively, that the sum of the tensions produced in the glass layers when the space between the glass layers is punctured/evacuated and the pins are pressed into the glass layers exceeds the level of tolerance of the glass layers so that they rupture. Thus, the pins do not function alone; they are dependent on the condition that the content between the glass layers is evacuated.
NO331150 discloses a crushable plug, for example of glass, which comprises a plurality of pin devices (spikes, claws, tips, points, compression ring) which are actuated to press radially into a glass layer so that it ruptures, said glass layer comprising pre-formed weakened points/areas that facilitate the crushing when the pin devices are pressed in against the plug. It is further disclosed in NO331150 that the weakened areas are formed by virtue of microfractures in the glass, such as those caused by honing. If one examines FIG. 3 in NO331150, one sees disclosed fractures that spread inwardly in the glass from the points of the pin devices. This type of fracture formation is what is assumed to have occurred when glass plugs of this kind are crushed. Since the glass layers are pulverized by crushing, it has thus not been evident how these glass layers were crushed. NO331150 shows a plug comprising one single glass layer. Although the description does not rule this out, NO331150 shows no embodiment comprising several glass layers. NO331150 therefore provides no teaching as to how the disclosed solution could potentially be adapted to a plug comprising more than one glass layer.
The present disclosure relates to a crushable or dissolvable plug comprising one or more glass layers, optionally other suitable materials, where the plug is removed without the use of explosives, with the disclosure providing a crusher mechanism that is predictable, safe and easier to utilize.